Initial Bearing Calculator
Updated recently with improved calculation accuracy and expanded examples.
Compute the initial true bearing from one lat/lon waypoint to another (the great-circle route's starting bearing).
Last updated: August 28, 2026
Author: OceanCalc Editorial Team · Publisher: Albor Digital LLC
Initial Bearing Calculator
Result
Initial true bearing (°)
51.2
Formula
Forward azimuth via spherical trigonometry (atan2 of sin÷cos terms)Model note: This calculator uses a spherical-Earth model to determine the initial bearing between the two coordinates; results are an approximation of navigation on the Earth's ellipsoid.
What is the Initial Bearing Calculator?
Compute the initial true bearing from one lat/lon waypoint to another (the great-circle route's starting bearing).
Does not apply variation/deviation; output is true bearing. This calculation uses spherical-Earth geometry and is an approximation of the corresponding ellipsoidal geodesic bearing.
bearing
Bearing is the direction from the observer or vessel to a referenced object or position, expressed as an angle from north.
Related Maritime Calculators
Overview
Bearing is the direction from the observer or vessel to a referenced object or position, expressed as an angle from north. A Initial Bearing Calculator is used in maritime navigation to perform precise calculations based on established nautical formulas. This tool allows you to apply your inputs to the stated nautical relationships using accurate and standardized methods.
Key takeaways
- Initial Bearing Calculator — Bearing is the direction from the observer or vessel to a referenced object or position, expressed as an angle from north.
- Formula — Initial bearing uses the standard forward azimuth formula between two geographic points on a sphere.
- How to use — Type your figures into the form; outputs refresh so you can compare cases quickly.
How to use
Type your figures into the form; outputs refresh so you can compare cases quickly.
Formula
Core relationship: Forward azimuth via spherical trigonometry (atan2 of sin/cos terms)
Initial bearing uses the standard forward azimuth formula between two geographic points on a sphere.
Does not apply variation/deviation; output is true bearing. This calculation uses spherical-Earth geometry and is an approximation of the corresponding ellipsoidal geodesic bearing.
Practical use cases
Initial Bearing Calculator: passage planning, crew briefings, instrument-to-chart unit checks, and verifying mental math when tired or in rough weather.
Tips for accuracy
- Match input units to your chart, GPS, or instrument before trusting the Initial Bearing Calculator.
- Cross-check important outputs with a second method or crew when visibility or motion is poor.
- Treat simplified models (waves, radar horizon, etc.) as estimates; real conditions vary.
Practical examples
- NYC to London initial bearing ≈ 51°
- Use with great-circle distance for route sketching
Frequently Asked Questions
Does bearing stay constant along the route?
No. Great-circle routes change bearing along the arc; this value is only the starting heading.
How accurate is this calculator?
It uses standard maritime formulas and noted approximations. Use it for planning and checks; confirm safety-critical decisions with official sources.
Can I use this on mobile?
Yes. Layouts are responsive for phones and tablets on deck or in the cockpit.
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These calculations are based on standard maritime navigation formulas used in seamanship, chart navigation, and marine route planning.
Results are estimates for educational purposes only and should not be used for real navigation decisions.